With a year to go before Pacific Rim hits theaters, Guillermo del Toro (Hellboy, Pan’s Labyrinth) hit Comic-Con with stars Charlie Hunnam, Ron Perlman, Rinko Kikuchi and Charlie Day to preview the giant robot-monster movie, inspired by the Japanese sci-fi pics he watched as a kid. His vision for the film? Dirty, epic, and realistic — so much so that Del Toro and his crew built functioning, practical robots and entire sets with hydraulics ("a huge engineering feat!"), putting his actors in the thick of the action rather than go the CG route. Del Toro called the experience “the best I’ve had on any film set in all my life.” Day remembered it slightly differently: “You tortured the f*** out of us!”

Developed with writer Travis Beacham, Pacific Rim is set years into a war between humans, piloting massive robots called Jaegers, and giant monsters from the sea that threaten to wipe out civilization. When his passion project At the Mountains of Madness folded, Del Toro turned his attentions to Pacific Rim, channeling an outsized amount of energy into making it his most ambitious project to date.

Given the Japanese sci-fi flicks that inspired the film — not to mention the upcoming Godzilla reboot bringing kaiju culture back into the mainstream — it’s easy to guess that genre aficionado Del Toro has crafted in Pacific Rim a love letter to said films. That love is abundant, but he insists that the pic will be forging its own path rather than referencing what’s come before.

“I wouldn’t compare it to a Godzilla film,” said Del Toro. “[I told my crew] we should not reference other movies. We should not go and re-watch Gamera or re-watch Gojira or War of the Gargantuans because we love them, right? So we said, let’s create the world that we’re doing. We should not be doing a referential film.”

So what should you know about Pacific Rim? Del Toro and his cast shared the essentials of the characters and robots vs. monsters universe of the film.

THE CHARACTERS

Hunnam plays Raleigh Antrobus, a former soldier called back into action who partners with Rinko Kikuchi's Mako Mori to co-pilot an obsolete Jaeger. "When you meet me in the beginning of the story I’ve suffered a giant loss, and not only has it killed my sense of self-worth, it’s also killed my will to fight and keep on going," Hunnam explained. "Rinko and a couple of people bring me out of retirement to try to help in this grand push. And I think that journey is a very relatable one; I think everybody in their life has fallen down and not felt like getting back up, but you have to no matter how difficult it is."

Kikuchi, who earned an Oscar nomination for Babel and appeared in Rian Johnson's Brothers Bloom, plays a newbie pilot who, like Raleigh, has also suffered great loss in her life. "The idea is that two people that are really, really hurt, can become one," Del Toro said of the partnership between the two characters. "Both in the robot metaphorically, and in life. They meet when they’re two empty pieces and connect almost like a puzzle."

Making the leap to big screen action is Day (It's Always Sunny in Philadelphia), as Newt Gotlieb. "You need big tough guys and strong guys and the people that you believe could fight and save the world," said Day, "and then in the case of my guy, you think, how does the sort of everyman who you’d think couldn’t fight his way out of a paper bag — how’s that guy going to contribute? What I think people will latch onto with my character is how flawed he is in his attempts to help save the world."

Rounding out the cast is Del Toro regular Perlman, whose Hannibal Chow is a black marketeer specializing in the illicit monster trade. "I have a relationship with the powers that be whereby I have the right to sell all these fallen monsters on the black market to rich people who have way too much money and are looking to collect rare and exotic, strange shit. So I have no moral compass, I have no scruples whatsoever — I’m just a profiteer, and in this case a war profiteer. But the war is not amongst countries, it’s a war against time for all of humanity."

THE SETS

In his pursuit for realism, Del Toro approximated faux-oil-splattered lenses and imperfect camera work to add believability to the visual experience. That desire for verisimilitude extended to his sets — some of which were outfitted with their own systems of shocks to make real the sort of effects that might otherwise be achieved with CG.

"We built a lot of things that were oversize and difficult in order to bring that tactile effect," Del Toro explained. "We built a whole street of Tokyo and we rigged it with pneumatic shocks, so every time the monster took a step the whole street would vibrate and the cars would jump and the walls would shake and the lampposts would shake and the air conditioning units would fall."

THE ROBOTS

With names like Crimson Typhoon and Cherno Alpha, the Jaegers of Pacific Rim are as tall as buildings and operate between two human pilots, connected by a neural link. "I wanted each robot to have a personality and for you to feel when the robot gets hurt, or when the robot wins," said Del Toro. "I want to make the audience feel for those machines as much as they feel for the humans — and also, frankly, for the kaiju."

Del Toro and his team designed the robots with real world mechanics in mind, with parts that served practical functions. And when it came time to film, he called on his cast to jump into their rigs for the aforementioned "torture." "The cockpit of the robot which is in the head, is almost three stories high," described Del Toro. "And we mounted it on hydraulic shakers so in battle every time they got hit, it would really hit. And I wanted to do it with the actors, I didn’t want to do it with the doubles."

"The first time they were in," he recalled, "Charlie came to visit the first group of actors — I won’t say who they were — and said, 'Crybabies!' This machine, which is the interface between the robots and them, flows with their bodies. It was a huge engineering feat. It was real. We could have done it CG, but why do that? [Laughs]"